U.S. patent number 7,254,306 [Application Number 11/130,753] was granted by the patent office on 2007-08-07 for optoelectronic component with curved waveguide with inwardly sloped sides.
This patent grant is currently assigned to Avanex Corporation. Invention is credited to Jean-Rene Burie, Genevieve Glastre.
United States Patent |
7,254,306 |
Burie , et al. |
August 7, 2007 |
Optoelectronic component with curved waveguide with inwardly sloped
sides
Abstract
The invention concerns semiconductor optoelectronic components
with ribbon-shaped waveguide supported by a substrate. According to
the invention the ribbon includes lateral sides and a light output
face, characterized by said ribbon including a portion curved by
more than two degrees in relation to the normal to the light output
face, and the lateral sides being inwardly sloped on the substrate.
The optoelectronic component may be an electro-optical modulator, a
semiconductor optical amplifier, a semiconductor laser or a
Mach-Zehnder-type interferometer. The component may also be formed
by joining two of these devices.
Inventors: |
Burie; Jean-Rene
(Bruyeres-le-Chatel, FR), Glastre; Genevieve (Linas,
FR) |
Assignee: |
Avanex Corporation (Fremont,
CA)
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Family
ID: |
34942609 |
Appl.
No.: |
11/130,753 |
Filed: |
May 17, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050271327 A1 |
Dec 8, 2005 |
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Foreign Application Priority Data
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May 17, 2004 [FR] |
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04 50972 |
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Current U.S.
Class: |
385/131 |
Current CPC
Class: |
G02B
6/12004 (20130101); G02F 1/025 (20130101); H01S
5/22 (20130101); G02B 2006/12097 (20130101); G02B
2006/12195 (20130101); G02F 1/2257 (20130101); H01S
5/101 (20130101); H01S 5/1014 (20130101); H01S
5/1085 (20130101) |
Current International
Class: |
G02B
6/122 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0651268 |
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May 1995 |
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EP |
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1 130 425 |
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Sep 2001 |
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EP |
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WO 01/17076 |
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Mar 2001 |
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WO |
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Other References
S J. Pearton, F. Ren, W. S. Hobson, C. A. Green, and U. K.
Chakrabarti, Dry Etching Of Submicron Gratings For InP Laser
Structures--Comparison Of HI/H.sub.2, CH.sub.4/H.sub.2 and
C.sub.2H.sub.6/H.sub.2 Plasma Chemistries, 8303 Semiconductor
Science and Technology, Sep. 7, 1991, No. 9, Bristol, Great
Britain. cited by other .
French Search Report, Application No. 0450972, dated Dec. 22, 2004.
cited by other .
EP Search Report, Application No. 05 300 377.8, dated Jun. 16,
2005. cited by other.
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Primary Examiner: Pak; Sung
Assistant Examiner: Rahll; Jerry T.
Attorney, Agent or Firm: Patterson & Sheridan, LLP
Claims
The invention claimed is:
1. A solid-state optoelectronic component with a waveguide in the
form of a tape supported by a substrate which constitutes a layer
of vertical optical confinement, the tape comprising: a light
emerging end, side flanks sloping inwards on said substrate, a
section curved by more than two degrees in relation to the
perpendicular to the light emerging end, wherein side flanks in
said curve section have a larger slope angle than side flanks in a
straight section of said tape, a layer of optical confinement
positioned above said substrate, and a contact layer positioned
above said layer of optical confinement, wherein side flanks in
said curve section have a larger slope angle than side flanks in a
straight section of said tape.
2. The optoelectronic component of claim 1, wherein said curved
section ends, at the emerging end of the waveguide, in a flared
shape.
3. The opto electronic component of claim 1, wherein said curved
section is flare-shaped.
4. The optoelectronic component of claim 1, wherein it constitutes
a Mach-Zehnder type interferometer.
5. The optoelectronic component of claim 1, wherein it is composed
of the association of several elements selected from among an
electro optical modulator, a solid-state optical amplifier, a
semiconductor diode and a Mach-Zehnder type interferometer.
6. The optoelectronic component of claim 1, wherein said vertical
layer of optical confinement is a quaternary semiconductor and said
contact layer is a ternary semiconductor.
7. The optoelectronic component of claim 1, wherein it constitutes
an electro optical modulator.
8. The optoelectronic component of claim 1, wherein it constitutes
a solid-state optical amplifier.
9. The optoelectronic component of claim 1, wherein it constitutes
a semiconductor diode.
10. A method for making a tape for an optoelectronic component, the
method comprising: placing a mask on a component, the component
comprising a substrate, an optical containment layer, a contact
layer, wherein the substrate and the contact layer comprises
arsenic and the mask defines at least one straight portion and at
least one curved portion; removing a portion of the contact layer
not protected by the mask by a ionic cleaning such that the
component includes at least one straight portion and at least one
curved portion, wherein the at least one curved portion is curved
by more than two degrees in relation to the perpendicular to a
light emerging end of the component; and soaking the component in a
hydriodic acid to form inwardly sloping side flanks on the optical
containment layer, wherein side flanks in said curved portion has a
larger slope angle than side flanks in the straight portion.
11. A method for making tape for a solid-state optoelectronic
component with a waveguide in the form of a tape supported by a
substrate comprising arsenic, the tape comprising a light emerging
end, side flanks sloping inwards on said substrate, a section
curved in relation to the perpendicular to the light emerging end,
wherein hydrogen iodide is used to make said sloping side flanks,
wherein side flanks in said curve section have a larger slope angle
than side flanks in a straight section of said tape.
12. The method of claim 11, wherein said substrate is an active
layer.
13. The method of claim 12 for making said tape supported by said
substrate, said tape forming a stacking of layers comprising at
least, starting from said substrate, a side layer of optical
confinement bearing no arsenic and a contact layer bearing arsenic,
wherein: a resin mask is photo-lithographically deposited on said
contact layer, said resin mask materializing the path of said tape;
the part of said contact layer not positioned under said layer of
resin is removed via ionic removal; said side layer of optical
confinement is chemically etched with a hydrogen iodide solution;
and said resin mask is removed.
14. The method of claim 13, wherein said hydrogen iodide solution
is pure hydrogen iodide.
15. The method of claim 13, wherein said side layer of optical
confinement is made of JnP.
16. The method of claim 11, wherein said curved section slopes more
than two degrees in relation to the perpendicular to the light
emerging end.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority benefit under 35 U.S.C. .sctn. 119
of French Application Serial No. FR 0450972, filed May 17, 2004.
The aforementioned related patent application is herein incorporate
by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention concerns a semiconductor optoelectronic component
consisting of a ribbon-shaped waveguide that is curved more than
two degrees with inwardly sloping sides.
2. Description of the Related Art
The type of optoelectronic component in the present invention is
illustrated in FIG. 1. In this figure, component 10 includes a
substrate 12 and an approximately rectangular parallelpiped
ribbon-shaped waveguide 14. When the component is formed by joining
a laser and a modulator, the length of the ribbon waveguide is
typically 600 microns and its width is 2.5 microns. The waveguide
includes lateral sides 16 and 18. The substrate and the waveguide
are formed by stacking layers of semiconductor material. The two
ends of the stack are covered by a metallic layer that provides
electric contact. Reduced to its simplest form, the stack is formed
by a first layer (the substrate), by a vertical optical confinement
layer (in direction Oyo) for waves propagating in the guide, by a
lateral optical confinement layer (in direction Ox) and by a
contact layer. This last layer is thin compared to the thickness of
the lateral optical confinement layer, which constitutes in fact
the semiconductor channel in which the waves are propagated.
Classically, two improvements have been separately made to this
component. On the one hand, the rectangular shape of the ribbon
guide has been curved to prevent interference from waves reflecting
on the output face of the component (and also possibly on the entry
face). This curvature has been obtained by chemical etching with
hydrochloric acid during manufacture of the component. On the other
hand, the lateral sides of the ribbon guide have been sloped inward
in relation to the vertical of the substrate in order to reduce the
electrical resistance of the component. Moreover, for this same
component a very slight curvature of the guide, at most of two
degrees, has been created. The slope of the lateral sides and the
very slight curvature were obtained by chemical attack with
hydrobromic acid. These features will be developed later in the
presentation of the invention.
However, using these techniques it is not possible to obtain a
curvature of the guide ribbon greater than two degrees and a slope
of the lateral sides for the same component. Chemical attack by
hydrochloric acid allows obtaining the curvature of the guide, but
not the slope of the sides and attack by bromohydric acid allows
obtaining the slope of the sides, but not a curvature of the
waveguide of greater than two degrees.
SUMMARY OF THE INVENTION
This invention provides a solution to this technical problem by
allowing obtainment of a guide that is curved by more than two
degrees and has inward sloped sides on the same optoelectronic
component.
More precisely, the objective of the invention is a semiconductor
optoelectronic component consisting of a ribbon-shaped waveguide
supported by a substrate, the ribbon including lateral sides and a
light output face, such that said ribbon includes at least one
portion curved by more than two degrees in relation to the
perpendicular to the light output face, and the lateral sides are
sloped inwardly on the substrate.
According to one implementation, the width of said ribbon, for a
same distance in relation to said substrate, is noticeably constant
along the ribbon and may, but not necessarily, terminate at the
output of the waveguide in a flared shape.
In another implementation, said curved portion has a flared shape
at the output of the waveguide.
The optoelectronic component may be, for example, one or the other
of the following devices: an electro-optical modulator, a
semiconductor optical amplifier, a semiconductor laser and a
Mach-Zehnder-type interferometer. The component may also be formed
by joining two of these devices, for example, a laser followed by
an electro-optical modulator.
The invention also concerns a procedure for creating said ribbon of
the optoelectronic component, consisting in the use of hydriodic
acid to produce the sloped lateral sides.
In one implementation of the procedure, said ribbon is supported by
a substrate and is formed by a stack of layers comprising, from the
substrate, at least one vertical optical confinement layer
containing arsenic, one lateral optical confinement layer not
containing arsenic and one contact layer containing arsenic, the
procedure consisting in the following: the deposit of a resin mask
on said contact layer, covering the trace of said ribbon, using
photolithography; the removal of the portion of said contact layer
not located under said resin layer, using ionic cleaning; the
chemical etching of said lateral optical confinement layer, using
hydriodic acid; and, the removal of said resin mask.
The hydriodic acid solution is preferably pure hydriodic acid.
BRIEF DESCRIPTION OF THE DRAWINGS
So that the manner in which the above recited features of the
present invention can be understood in detail, a more particular
description of the invention, briefly summarized above, may be had
by reference to embodiments, some of which are illustrated in the
appended drawings. It is to be noted, however, that the appended
drawings illustrate only typical embodiments of this invention and
are therefore not to be considered limiting of its scope, for the
invention may admit to other equally effective embodiments.
FIG. 1 schematically represents the general architecture of the
components concerned by the invention,
FIG. 2 is an above view of an example of implementation of the
component,
FIG. 3 is an above view of two other examples of implementation of
the component,
FIG. 4 is a cutaway view according to an xOy plane of the
components of FIGS. 2 and 3,
FIGS. 5 to 7 illustrate the procedure of implementation of the
component.
DETAILED DESCRIPTION
FIG. 2 schematically represents an above view, according to the Oy
axis, of a mode of implementation of the invention that concerns
the first improvement mentioned above, the curvature of the
waveguide. In this figure, the waveguide 20, supported by substrate
22, includes a straight portion 24 followed by a curved portion 26
directed toward output 28 of the guide, which constitutes the light
output face. The sides of the guide ribbon 20 are sloped inward in
relation to the vertical (the surface of the substrate is in the
zOx plane and the vertical is thus according to the Oy axis). The
width of said ribbon (20), for a same vertical distance (according
to the Oy axis) in relation to said substrate (22), is
approximately constant along said ribbon. In other terms, the two
upper edges of the waveguide are approximately parallel as
represented in FIG. 2.
The curved portion 26 makes it possible to reduce, or even delete,
the waves reflected by the output face 28 and thus avoid
perturbations caused by a coupling in the component of reflected
waves with waves propagated toward the output (in the Oz
direction). When the component is a semiconductor optical
amplifier, it is useful to curve the guide at its two extremities
in order to eliminate perturbations due to reflected waves at the
two extremities.
FIG. 3A shows another form of implementation, in an above view, of
a curved guide. The guide ribbon 30, supported by the substrate 32,
includes a straight portion 34 followed by a curved portion 36 but
here with a flared shape. In the second implementation shown from
above in FIG. 3B there is no straight portion. The ribbon guide
34a, supported by substrate 32a, has only lateral sides that
diverge in relation to each other (above view).
According to the prior art, the curvature of the waveguide is
created primarily by chemical cleaning with hydrochloric acid.
According to the invention, hydriodic acid is used.
The second improvement mentioned above, illustrated in FIG. 4,
consists in giving an inward slope to the lateral sides of the
guide. In FIG. 4, which is a cutaway view of the optoelectronic
component in FIG. 2 or 3, according to an xOy plane, the guide
ribbon, supported by the substrate 22 (FIG. 2) or 32 (FIG. 3), is
formed by stacking a lateral optical confinement layer 40, a
contact layer 42 and a metallic layer 44 for electrical contact.
The diagram is not to scale, the whole of layers 42 and 44 is very
thin (on the order of 0.3 .mu.m) compared to the thickness of layer
40 (on the order of 3 .mu.m). The lateral sides 46 and 48 form an
inward angle w in the xOy plane. The purpose of this slope is to
reduce the electrical resistance of the component, which is due to
the electrical resistance of the interface 50 between the metallic
layer 44 and the contact layer 42. This electrical resistance R is
equal to R=p l/S where p is the resistivity, l is the length and S
is the surface of the interface. By increasing surface S,
electrical resistance R is thus reduced. The reduction of
resistance R allows reduction of electrical consumption and heating
of the component. It also allows increasing bandwidth. However, for
the purposes of guiding optical waves, the width 52 at the base of
the guide may not exceed a certain value. This width is on the
order of several microns, for example, 2.5 microns. There are thus
two opposing requirements: on the one hand, to obtain the weakest
electrical resistance R by increasing the surface S and, on the
other hand, not to exceed certain values for the width 52 at the
base of the waveguide. The slope of the lateral sides 46 and 48
provides a good compromise to these conflicting requirements.
According to the prior art, the slope of the lateral sides is
obtained by chemical attack, using hydrobromic acid. The attack by
hydrobromic acid also makes it possible to obtain a very slight
curvature of the guide ribbon that does not exceed two degrees.
Beyond this value, a severe attack on the sides occurs that
destroys the desired slope and makes the component unusable.
According to the invention, the slope of the lateral sides is
obtained by chemical attack using hydriodic acid. The use of this
acid thus makes it possible to obtain both the curvature of the
waveguide, with a curvature greater than two degrees, and the slope
of the lateral sides, which the prior art does not allow.
FIGS. 5 to 7 illustrate the procedure for creating the curvature of
the waveguide and the slope of the lateral sides. In these figures
only the layers necessary to understand the procedure are shown.
For example, the metallic contact layers do not appear. The
component includes successively a layer 54, a lateral optical
containment layer 56 and a contact layer 58. Layer 54 is preferably
made of a quaternary material such as GalnAsP, whereas the contact
layer 58 is preferably made of tertiary material such as GaInAs.
The lateral optical confinement layer 56 is preferably formed by
p-type doped InP. It is noted that layers 54 and 58 contain
arsenic, an element that blocks chemical etching by hydriodic acid,
whereas layer 56 does not contain any arsenic. A resin mask 60 is
deposited by photolithography on contact layer 58, covering the
trace of the waveguide. This resin mask thus takes the shape
desired for the waveguide, seen from above. This shape includes at
least one portion that forms an angle with the normal on the output
facet, as represented, for example, in FIG. 2 or 3.
The next ste
in the procedure (FIG. 6) consists in ionic cleaning of the contact
layer 58. The portions of this layer not located under the resin
mask, thus not protected, are removed. If a metallic contact layer,
platinum for example, were placed between the resin mask and the
contact layer, the unprotected portions of this metallic layer
would also be removed.
The component is then soaked in a hydriodic acid solution in order
to form the inward slope of the lateral sides of the waveguide
(FIG. 7). Preferably, the solution is pure hydriodic acid. This
acid only etches the InP layer 56, the presence of arsenic in
layers 54 and 58 blocking the chemical etching. This treatment with
pure hydriodic acid takes about one minute, several minutes at
most. The slope angle w of the inward sides is determined by the
orientation of the crystal plane of the InP monocrystal material.
This angle is approximately 54 degrees when the crystal plane is
parallel to the yOz plane. In the curved portion of the waveguide,
the crystalline plane revealed by the hydriodic acid etching is no
longer the same; it follows that the slope angle w increases with
the angle of curvature. The sides are thus more inward-sloping in
the curved portion or portions of the guide.
The invention thus allows creation of an optoelectronic component
that includes both inward sloping sides and at least one curved
portion with an angle greater than two degrees. This component may
be an electro-optical modulator, a semiconductor optical amplifier,
a semiconductor laser or a Mach-Zehnder-type interferometer. It may
also be constituted by joining two of these devices, for example a
semiconductor laser followed by an electro-optical modulator.
The examples of implementations described demonstrate a component
that has a straight waveguide portion followed by a curved portion.
The shape of the guide may be more complex. For example, in the
case of a semiconductor optical amplifier, the two ends of the
guide are advantageously curved so as to prevent reflections on the
two faces. The guide includes thus a curved portion, a straight
portion and a curved portion or a straight guide with a strong
slope in relation to the output faces (typically 7.degree. to
10.degree.).
While the foregoing is directed to embodiments of the present
invention, other and further embodiments of the invention may be
devised without departing from the basic scope thereof, and the
scope thereof is determined by the claims that follow.
* * * * *